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C J Knowles

Publications and source records attributed to C J Knowles.

52 records · Page 3Linked to original sources
PubMed1969

Cytochrome and ubiquinone patterns during growth of Azotobacter vinelandii.

After synthesis during the early log phase, the concentrations of ubiquinone and cytochromes did not vary during the growth cycle of Azotobacter vinelandii, when grown with either high or low aeration on nitrogen-free or urea-containing media. The level of aeration had no effect on the concentrations of the electron carriers synthesized, but affected the growth rate. On urea-containing medium, the concentration of cytochrome a(2) was low, but it was synthesized at a linear rate when the bacteria were transferred to nitrogen-free medium. A. vinelandii was shown to utilize sufficient medium urea to account for all of the cell nitrogen. Growth on urea-containing medium with an oxygen atmosphere resulted in low growth yields, and cytochromes c(4) + c(5) were not synthesized; the concentrations of ubiquinone and cytochromes b(1), a(1), and a(2) were only 12 to 18% of the values for growth on nitrogen-free medium with high aeration.

Air↗
PubMedDate not supplied

Effect of metal complexation on the bioavailability of nitrilotriacetic acid to Chelatobacter heintzii ATCC 29600.

Many polluted sites contain a mixture of organics and heavy metals. Nitrilotriacetic acid has been chosen as a model organic compound to study the effect of metal binding on organic bioavailability and degradation of organics. The effect of varying the ratio of metal to nitrilotriacetic acid on its utilisation has been examined using the gram-negative bacterium Chelatobacter heintzii ATCC 29600. The following parameters of substrate utilisation were examined: growth, degradation, respiration, mineralisation and nitrilotriacetic acid uptake. Complexation of nitrilotriacetic acid by Cu(II), Ni(II), Co(II) and Zn(II) prevented utilisation of nitrilotriacetic acid by C. heintzii; complexation to Fe(III) or Mn(II) did not. The pattern of inhibition was consistent with a 1:1 stoichiometry of metal binding to nitrilotriacetic acid. Inhibition was not due to metal ion toxicity, but was a result of metal-nitrilotriacetic acid complexes being recalcitrant to degradation. In addition, the effect of complexing (phosphate) and non-complexing (PIPES) buffers on bioavailability was examined: Co and Zn prevented degradation of nitrilotriacetic acid in PIPES buffer, but not in phosphate buffer. This was due to the removal of Co and Zn from solution by phosphate precipitation, leaving nitrilotriacetic acid uncomplexed. The results demonstrated that metal-organic complexation can alter the bioavailability of organic pollutants and may also modulate the toxicity of heavy metals.

Biodegradation, Environmental↗
PubMedDate not supplied

Effects of auricular acupuncture-like transcutaneous electric nerve stimulation on pain levels following wound care in patients with burns: a pilot study.

This study was designed to test the hypothesis that auricular acupuncture-like transcutaneous electrical nerve stimulation would significantly reduce the pain experienced by patients with burns immediately after wound debridement, other wound care, and dressing changes. Subjects were 11 inpatients at the University of Alabama Hospital Burn Unit. A two-period crossover design was used, and each patient received one experimental treatment consisting of bilateral acupuncture-like transcutaneous electrical nerve stimulation to six ear points and one control treatment consisting of a placebo pill. The Visual Analogue Scale was used as a measure of pain and was completed immediately before and after treatments and at 15, 30, and 60 minutes after treatment. A two-factor repeated measures ANOVA indicated significant effects of measurement time (p less than 0.001) and treatment by time (p = 0.002). Post hoc analysis revealed significant differences (p less than 0.05) between experimental and control conditions at all times after treatment but not at pretreatment baseline. These results indicate that auricular acupuncture-like transcutaneous electrical nerve stimulation may be an effective pain management technique in patients with burns.

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